Tire Size Box

165/80R15 vs 185/80R15

185/80R15 compared with 165/80R15

+5.0% diameter, +0.8" width

185/80R15 is 26.65" tall vs 25.39". More than the 3% rule of thumb, so check carefully before switching.

25.4"15" rim5.2"6.5" wide
165/80R15 (solid) compared with 185/80R15 (dashed outline), drawn to scale

With 185/80R15 tires, when your speedometer says 60 mph you are really going

63.0 mph

185/80R15 is +1.26 inches (+5.0%) in overall diameter. That is more than the 3% most shops and makers recommend.

165/80R15185/80R15Difference%
Overall diameter25.39"26.65"+1.26"+5.0%
Section width6.50"7.28"+0.79"+12.1%
Sidewall height5.20"5.83"+0.63"+12.1%
Circumference79.78"83.73"+3.96"+5.0%
Revolutions per mile794.2756.7−37.5−4.7%

Speedometer difference

If your vehicle came with 165/80R15 and you fit 185/80R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.0 mph+1.0 mph
30 mph31.5 mph+1.5 mph
40 mph42.0 mph+2.0 mph
50 mph52.5 mph+2.5 mph
60 mph63.0 mph+3.0 mph
65 mph68.2 mph+3.2 mph
70 mph73.5 mph+3.5 mph
75 mph78.7 mph+3.7 mph
80 mph84.0 mph+4.0 mph

Each size on its own

Questions

Which is bigger, 165/80R15 or 185/80R15?
185/80R15 is taller by 1.26 inches (26.65" vs 25.39"). 185/80R15 is wider by 0.79 inches.
Can I replace 165/80R15 with 185/80R15?
It is not recommended without checking carefully. The diameter difference is +5.0%, more than the 3% most shops and makers allow. It will throw off the speedometer and may affect ABS, stability control and clearance.
How much will 185/80R15 change my speedometer?
When your speedometer reads 60 mph with 185/80R15 fitted (calibrated for 165/80R15), your real speed is 63.0 mph. Your odometer will under-count miles by about 5.0%.
Will 185/80R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.63 inches of ground clearance at the axle.

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